JPH02258160A - Production of aluminum heat exchanger having excellent pitting resistance - Google Patents

Abstract

PURPOSE:To obtain the heat exchanger having excellent pitting resistance by applying Zn powder in the state of mixing the same with a synthetic resin binder on the surface of an Al (alloy) tubular material to a specific thickness, using the fluoride of K and Al as the essential components as a flux and subjecting the coating to a heating treatment for brazing. CONSTITUTION:The Zn powder is applied in the state of mixing the same with the synthetic resin binder to 10 to 30mum thickness on the surface of the Al (alloy) tubular material. The diffusion of the above-mentioned Zn powder to the surface part of the Al alloy tubular material is accelerated by the effect of the fluoride of the K and Al, such as K3AlF6, and the generation of the pitting is prevented over a long period of time. The Zn is diffused deeply into the surface part of the tubular material at the time of the heating treatment for brazing by the formation of the coating layer by the synthetic resin binder of the Zn powder and the use of the flux essentially consisting of the fluoride of the K and Al. The pitting resistance is thus improved.

Description

Detailed Description of the Invention [Industrial Application Field] This invention provides aluminum heat treatment with excellent pitting corrosion resistance by promoting the diffusion of Zn into the surface of A, l) alloy tube material during brazing heat treatment. The present invention relates to a method of manufacturing an exchanger (hereinafter referred to as an Al heat exchanger).

[Conventional technology]

Conventionally, Al heat exchangers such as automobile radiators, air conditioners/condensers, and evaporators have generally been manufactured using (a) 11 or AΩ alloys such as JIS Al050 materials, Al1100 materials, and JIS Al 3003 and 3102 materials; A pipe material is formed by extrusion processing, and this straight pipe material, or a meandering pipe material by bending it, (b) Same < 3003 material, 3102 February, 3202
Corrugated processing consisting of a brazing sheet made by cladding a brazing material made of Aj7-3t alloy such as E 4343 or 4045 on the face or both sides of a core material made of 11 alloy such as E 95144. (e) This combination includes NaC, 17, and LiCΩ.

After applying a flux whose main component is chloride such as ZnC (12 or KCΩ) mixed with water, (d) At a temperature of 580 to 610°C in the atmosphere for 3 to 30 minutes.
Brazing heat treatment is performed under the condition of holding for 20 minutes (
It is well known that it is manufactured by the main steps a) to (d).

In addition, for the purpose of imparting pitting corrosion resistance to the heat exchanger described above, a Zn layer is formed on the surface of the above-mentioned 11 or Al alloy tube material by thermal spraying or plating, and the brazing and heating of this Zn layer is performed. It has also been proposed to electrochemically render the surface of the control surface corrosive by diffusion during treatment, thereby making it completely corroded, thereby preventing the occurrence of pitting corrosion.

[Invention or problem to be solved]

However, in the above-mentioned Al heat exchanger subjected to the Zn diffusion treatment, Zn does not diffuse sufficiently to the tube material surface, so when the Al heat exchanger is placed in a particularly severe corrosive environment, At present, it is impossible to avoid pitting corrosion from occurring relatively early.

[Means to solve the problem]

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to promote Zn diffusion in Al heat exchangers and thereby suppress the occurrence of pitting corrosion over a long period of time. A, 9 or A, l) Z formed on the surface of the alloy tube by conventional thermal spraying or plating.
Instead of the n layer, Zn powder, specifically 10 to 300 μm
Zn powder having an average particle size of At the same time, in place of the conventionally used chloride-based flux, KAΩF
When a flux containing K and Al fluorides as the main components, such as +KAlF4, is used in a state mixed with water, the K and All
Since the fluoride acts to promote the diffusion of Zn powder to the surface of the tube material, Zn diffuses deep into the surface of the tube material, and as a result, the Al heat exchanger is exposed to severe corrosive environments. However, they discovered that it exhibits excellent pitting corrosion resistance over a long period of time.

Therefore, the present invention has been made based on the findings mentioned in section 2 above, and is based on the findings described in section 2 above. A corrugated Aβ alloy fin material consisting of a brazing sheet clad with Al-8i alloy brazing material on both sides is combined, and after applying flux mixed with water to this combination, a brazing heat treatment is performed. When manufacturing an Al heat exchanger by the main process consisting of
The above flux is coated to a thickness of l.
During the brazing heat treatment, K and A in the flux are used.
This method is characterized in that the diffusion of the Zn powder into the surface of the A, 9 alloy tube material is promoted by the action of the fluoride of l, thereby preventing the occurrence of pitting corrosion over a long period of time.

In addition, in the method of this invention, the thickness of the coating layer of Zn powder is limited to 10 to 300 μm, because if the thickness is less than 10 μm, Zn will not be sufficiently diffused to the surface of the pipe material, whereas if it exceeds 300 μm, Even if the thickness is made thicker, no further Zn diffusion effect will be obtained, and this is due to economic considerations.

〔Example〕

Next, the method of the present invention will be specifically explained using examples.

Each pipe material has a JIS standard composition shown in Table 1, and is formed by hot extrusion. Width: 30 m
mX thickness: 5n++ aX thickness: 0. [A 4-hole pipe material was prepared by bending a flat pipe having a size of 1 mm into a meandering shape, and as a fin material, JI as shown in Table 1 was prepared.
Thickness: 0.1 [i+
A corrugated brazing sheet of n+n was prepared, and first, Zn powder was applied to the surface of the various pipe materials mentioned above under the conditions shown in Table 1, and the temperature was kept at 50°C for 5 minutes in the air. The Zn powder may be applied to the straight pipe material before bending or to the assembled pipe material, especially during hot extrusion molding of the pipe material. During the cooling process, preferably the tube material is
(The drying step can be omitted if the process is carried out after the heat exchanger has been cooled to 200°C).Then, after combining these tube materials and fin materials into the shape of a heat exchanger, the combination shown in Table 1 is applied. K and Al
The fluoride mixed with water is spray coated to a thickness of 15 μm, and finally, this is subjected to brazing heat treatment at a temperature of 600°C for 5 minutes in a nitrogen atmosphere of 7 to 10 torr. By carrying out each of the methods 1 to 6 of the present invention, 11
A heat exchanger was manufactured.

For the purpose of comparison, instead of applying the Zn powder, a Zn layer was formed by ordinary thermal spraying or immersion hot plating, and various chloride fluxes shown in Table 1 were applied as flux to a thickness of 15 μm. An AjJ heat exchanger was manufactured by carrying out Conventional Methods 1 to 4 under the same conditions except for spraying to a thickness of .

Next, for the various Al heat exchangers obtained as a result, we determined the average Zn diffusion depth at 10 predetermined locations on the surface of the tube material, which is a structural member, and determined the CASS
A test was conducted and the time required for pitting corrosion to occur was determined as Δ1. The results of these measurements are shown in Table 1.

〔Effect of the invention〕

As is clear from the results shown in Table 1, the method 1 of the present invention
According to ~6, compared to conventional methods 1~4, with easier operation,
Moreover, it is possible to manufacture an Al heat exchanger in which Zn is diffused deep into the surface of the control without requiring large-scale equipment. The heat exchanger exhibits significantly superior pitting corrosion resistance over a long period of time compared to Al heat exchangers manufactured by conventional methods 1 to 4.

As described above, according to the method of the present invention, a coating layer of Zn powder is formed using a synthetic resin binder, and K and A
By using a flux mainly composed of 1 fluoride,
During brazing heat treatment, Zn can be diffused deep into the surface of the tube material, making it possible to manufacture All-Al heat exchangers that exhibit excellent pitting corrosion resistance over a long period of time, making it industrially useful. This brings about a great effect.

Mitsubishi Aluminum Co., Ltd. 1 other person

Claims (1)

[Claims] (1) Corrugated processing consisting of a brazing sheet made by cladding an Al-Si alloy brazing material on one or both sides of an Al alloy core material on an extruded straight pipe or meandering Al or Al alloy pipe material by bending. In the method of manufacturing an aluminum heat exchanger, the main process is to combine the Al alloy fin materials of the above, apply flux mixed with water to this combination, and then perform brazing heat treatment. Zn powder mixed with a synthetic resin binder is coated on the surface with a thickness of 10 to 300 μm.
The above flux was applied to a thickness of K.
During the brazing heat treatment, K and A in the flux are used.
Due to the action of the fluoride in the Zn powder, Al or Al
A method for manufacturing an aluminum heat exchanger with excellent pitting corrosion resistance, characterized by promoting diffusion to the surface of an alloy tube material.